To prepare for his close-up, the 19-year-old is training at an Anchorage gym.

A formal agreement hasn’t been reached with the online magazine, but the photo shoot is a “foregone conclusion,” said the lawyer, Rex Butler.

Publication of the photos could embarrass Palin, who has been mentioned as a possible GOP presidential candidate in 2012.

After Palin was chosen as John McCain’s running mate, Johnston was thrust into the national spotlight when she announced her unwed daughter was pregnant and the couple would marry. But they broke up after the birth of their son, Tripp, in December.